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Truss Analysis Wizard

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Solve 2D trusses with a live FEA engine. Set nodes, fixities, and members in-browser, and get shear, moment, and deflection results as you work. Covers roof, floor, and custom truss geometries with nothing to install.

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Worked example

A roof truss is to be designed in Australia. The calculation details of this worked example can be found here.
  • Fink Truss type with 8 meters wide, 2.5 meters height, and a 400 millimeter overhang. Please check the diagram in Summary section to confirm the dimensions.\
  • Timber components, with both top and bottom chords 140x45 MGP10, and web members 70x45 MGP10, all oriented about their major axes. Note that if you change the member orientation, the bending stiffness (EI) in the table Member Data is updated.\
  • Factored dead plus live load of 0.7 kN/m on the top chords, and a factored ceiling dead load of 0.1 kN/m on the bottom chord (vertical loads). You can check the diagram under the Summary section to confirm if the loads are correctly applied.\
  • Factored wind load of 0.45 kN/m on the top chords
  • The figure below shows the load table, don’t forget to check Yes for including self-weight.
  • Under Summary, you can check all results. For axial forces, for example, the results shown in the diagram are confirmed in the table Overall Results by Member Type.
  • The displacements and support reactions are also shown in diagrams and tables.
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Method & scope

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Scope

The Calcs.com Truss Analysis calculator allows users to input the geometry of some common truss types and specify the load conditions on the truss. It then determines the cumulative load applied, support reactions, bending moment, shear and axial forces, extension and displacement for each chord of the truss. Component members of the truss may then be designed by creating a new “Design Only” calculation, and linking it to the truss analysis calculation. The sheet has 3 main input sections, plus the Summary results section:
  1. Truss/Frame Geometry
  2. Member Selection
  3. Distributed Loads on Chords
  4. Summary
This article will explain the expected input parameters in each of those sections and present a worked example of a truss analysis calculation.

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Calculation method

The Truss Analysis Wizard uses a direct stiffness finite element analysis (FEA) engine to solve any planar 2D truss. You define the geometry, node coordinates, member connectivity, support fixities, and loads, and the solver assembles and inverts the global stiffness matrix to return forces and displacements simultaneously across every member.
Geometry and member modeling
Each member is modeled as a two-node axial bar element with user-specified cross-section area (A) and elastic modulus (E). The calculator supports a library of preset truss configurations, Flat Warren, Flat Pratt, Flat Howe, Flat Brown, King Post, Queen Post, Single Fan, Simple Fink, and Fink roof trusses, as well as fully custom node and element definitions. For non-custom configurations, straight chord regions are treated as continuous members rather than pin-jointed segments; this is more accurate but means results may differ slightly from a traditional hand analysis.
Stiffness assembly and solution
The solver assembles the global stiffness matrix from the individual element stiffness contributions, applies boundary conditions at pinned and roller supports, and solves the resulting system of linear equations for nodal displacements. Member end forces are back-calculated from the displacements using the element stiffness relation.
Sign conventions and outputs
  • Positive bending moment indicates that the bottom or right side of the member is in tension.
  • Positive axial load indicates a compressive load (compression-positive convention).
Results reported for each member and element include:
  • Axial force, tension or compression demand in each member
  • Shear force and bending moment envelopes along each element
  • Nodal displacements and support reactions
Output tables include overall results by member type, maximum displacements by member, support reactions, results by element number, and results by node number.
Load application
Distributed loads can be applied to chord members. For preset configurations, loads are specified over the chord length; the FEA engine converts these to equivalent nodal contributions automatically. Advanced users can also apply loads directly by element number for non-standard cases. Multiple load cases are evaluated and an envelope of governing demands is reported.
Linking to design calculators
The Truss Analysis Wizard is an analysis-only calculator. After solving, member force demands (moment, shear, axial) can be linked directly to Design Only calculators, such as timber, steel, or cold-formed steel beam calculators, so each member is checked against the relevant code without re-entering geometry or loads.

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How to use it

1

Truss/Frame Geometry

A. Truss TypeCalcs.com supports a variety of truss types including flat trusses, roof trusses and scissor trusses. For a full list of all the truss types available please refer to our Truss Types article.A visual diagram of the selected truss type will appear in the summary section, which will update as you input height, width, and loading parameters.B. Total Truss HeightThe vertical distance from the highest point of the truss to the lowest point of the truss as measured in millimeters (or feet if you are using the Imperial unit system).C. Total Truss WidthThe horizontal distance from the left-most point of the truss to the right-most point of the truss as measured in millimeters (or feet if you are using the Imperial unit system).D. Additional PropertyOne or more additional properties may also appear, depending upon the specific truss type you’ve chosen. If you are ever unsure as to what it is asking for, simply click on the property name to obtain a drop-down explanation.
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Member Selection

A. Truss Material / Linked Cross-SectionsThe material out of which your truss has been made. You will be given a drop-down menu, from which you can select the relevant material.For Linked Cross-Sections, refer to Section 5 of this article.B. Size and Orientation of Truss MembersNote that this Truss Analysis Wizard is for analysis purposes only. Selecting the right cross-section directly affects the results of the calculations, as they have different stiffnesses and self-weight. As previously mentioned, if you wish to design this member (i.e., pass/fail per code), you will need to create a ‘Design Only’ calculation and link to this truss analysis calculator (see Section 5).Top ChordAn inclined or horizontal member that marks the upper edge of the truss.Bottom ChordAn inclined or horizontal member that marks the bottom edge of the truss.Web Member(s)Member/s that join the top and bottom chords to form triangular patterns to give truss actions.Cross-sectionThe size of the top chord, bottom chord and web members need to be specified from drop-down menus. The drop-down menus will automatically display relevant industry-standard sizes for the truss material you specified. You can also use the member selector function to choose a member size. Note that the section sizes and types shown do change depending upon the building standard you are using for the current project. That is, a project using the Australian building standard will show standard Australian sections, and a project using the United States building standard will show standard US sections.OrientationThe orientation of the top chord, bottom chord and web members need to be specified as to whether they are oriented about their major axis or minor axis.
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Distributed Loads on Chords

A. Total Distributed LoadsFor the first two sections, the total vertical distributed loads for the top chord and bottom chord need to be specified in kN/m (or plf if you are using the Imperial unit system). Depending upon the type of truss selected, inputs may also be available for loads that are perpendicular to the top chord (not vertical i.e., gravity versus aligned loading conditions).Please note that the subsequent section “Advanced Loads (by Element Number)” can be used to enter loads for individual members, point loads, and angled loads - but most analyses should not require this.B. Self-WeightYou can choose whether or not to include the self-weight of the truss in calculations. The default has been set to include the self-weight of the truss.
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Summary

On top of the summary section is a diagram of your truss. The display of this diagram can be changed to show loads and supports, bending moment, shear forces, axial forces, extension of members, displacement of members and reaction forces at supports. This feature is illustrated below.The truss diagram is followed by tables that summarize the calculations and indicate the worst case maximum moments, shears, axial forces, deflections, and extensions for each member type defined. The designer will then use these values to ensure all selected members, connections, etc. are designed to withstand these worst-case loading conditions per code as well as the designer’s judgment. If you would like to link to a ‘Design Only’ calculator to complete your truss design in Calcs.com, see below.
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Designing Components by Linking New Calculators

Typically, once a truss is analyzed, the components will also need to be designed. This may be done in Calcs.com by the following procedure:
  1. Select “Add New Calculation” in the left sidebar
  2. Add a “Design Only” calculator for the appropriate material (for example, “Timber Member (Design Only)”)
  3. Next to the loads table in this new calculator, click on Link
  4. In the modal that pops up, select the truss analysis calculation, and then the component of the truss you wish to design (for example, “Top Chord”)
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  5. Complete the rest of the design as normal, referring to the help documentation for the specific material.
Note that loads on the member will automatically update when you update the truss analysis calculation. However, at this time, the specific section used in the analysis is not linked between the analysis module and the design module and must be selected independently in both calculations. For example, if you select a 140x45 MGP10 in this ‘Timber Beam (Design Only)’ calculator, you will need to manually ensure that a 140x45 MGP10 is also selected in your Truss Wizard Analysis calculator. Not to worry! Two-way linking will be coming in the future for Calcs.com - our engineering team is already hard at work on this feature.

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Common questions

The Truss Analysis Wizard uses a direct stiffness finite element analysis (FEA) engine. Each truss member is modeled as a two-force axial element. The solver assembles the global stiffness matrix, applies boundary conditions at pinned and roller supports, and solves for nodal displacements and member forces simultaneously.
Key inputs are node coordinates (x, y), member connectivity (start node, end node), support fixity at each node (pinned, roller, or free), member cross-section area and elastic modulus, and applied nodal loads (force magnitude and direction). You can define any planar truss geometry, roof, floor, Pratt, Howe, or fully custom layouts.
Outputs include axial force in every member (tension or compression), nodal displacements, and support reactions. Force diagrams and displacement plots update live as you edit geometry or loads. Results are printable in a structured report for submission or record-keeping.
Yes. The calculator is geometry-agnostic, nodes can be placed anywhere in the plane, and members can connect any two nodes. This allows Pratt, Howe, Fink, Gambrel, arch, and multi-bay configurations. There is no limit on the number of nodes or members within the platform.
Distributed loads on chord members must be converted to equivalent nodal loads at the panel points before entry. Divide the distributed load by the panel spacing to get point loads at each intermediate node. For roof trusses under uniform snow or dead load, this means applying equal vertical forces at each top-chord node based on tributary length.

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Next steps

Analyze a Portal Frame in Calcs.com

Analyze single- or multi-bay 2D portal frames with FEA. Flat, gable, arch and tied geometries, with moment, shear, axial and displacement results.

Design a Timber Member (Design Only) to AS 1720.1:2010 (Amdt 3)

Design timber truss chords, frame members and rafter ties to AS 1720.1:2010 (Amdt 3), with combined bending, axial and shear checks.

Create and Use a Custom Section in the Custom Truss Analysis

Learn how to build a custom truss layout, define member types, create a custom cross-section, and link it into the Custom Truss Analysis calculator.

Link Design Calculators to Truss & Portal Frame Analysis

Link Design Only calculators to Truss Analysis and Portal Frame Analysis results to check member capacity against the analysis forces.